Combustion of pulverized or similar fuel



Jan. 19, 1932. s. M. FINN 1,841,587

COMBUSTION OF PULVERI ZED OR SIMILAR FUEL Filed Dec. 3. 1927 4Sheets-Sheet l INVENTOR:

J: 3% M. FM L BY I 5 09M, K MMH &W

80 f ATTORNEYS.

Jan. 19, 1932. s, M. HNN 1,841,587

COMBUSTION OF PULVERIZED OR SIMILAR FUEL Filed Dec. gs. 192'! 4 Sheets-Sheet 2 IN VEN TOR.

M- Fv'wn,

BY I gw Kmwq away A TTORNEYS.

Jan. 19, 1932. s. M. FINN 1,841,587

coususnou orruLvsRIzEn on SIMILAR rum.

Filed Dec'. 3. 192'! 4 Sheets-Sheet 3 a? 24 a a 4 I Y 75 P WWW y (MW/1 ATTORNEY'.

Jan. 19, 1932. s, FlNN 1,841,587

COMBUSTION 0F PULVERIZED 0R SIMILAR FUEL Filed Dec. 3. 1927 Q 4Sheets-Sheet 4 IN VEN TOR.

33414 M. Fm

BY PW,WMMZJ9 xfww A TTORNEYS Patented Jan. 19, 1932 UNlTED STATES PATENTOFFICE srnrnnn I. rim, or Jsnssr crrr, NEW messy, assrenoa Tb mamnon-cnmxnnme rummcn :mocx comm, me, or new YORK, n. Y.

COMBUSTION OF P'UlIN'E-RIZED OR SIMILAR FUEL Application filed DecemberThis invention relates to combustion of pulverized or similar fuel,having particular reference to a system of burning pulverlzed coal oranalogous'fuel in suspension in alr; andthe invention includes notmerely the novel furnace hereindisclosed, the burner thereof, and otherfeatures of apparatus, but also the novel described method of combustionof such fuel, and features of operation and control. The presentinvention, although the disclosed embodiment is designed especially foruse in boiler furnaces, is of wider utility, and availablefor variousindustrial or other combustion systems.

The general object of the present invention is to afiord apparatus forand method of combustion of pulverized or analogous fuel which will beof increased efliciency and durability, and more adaptable andconvenient of control. A particular object is to afford a system,including apparatus and method, of fuel combustion wherein the fuel,

carriedin a stream of primary air, is supplied with' preheated secondaryair at the combustion point in a practical and advantageous manner.Afurther object is to afford a combustion system for suspended fuelwherein the fuel laden primary. air and the secondary air are combinedand delivered whirlingly into the furnace in such a manner as to producethe short,.wide-angled and turbulent type of flame which has been foundto be very effective with steam boiler furnaces. A further object is toafford a burner having a driven fan orsuction means operating inapredeterminedcooperative manner upon both the fuel laden primary streamof air and the secondary air, so that the relation of the two and thetype of flame ma be preserved when adjusting the rates of eed. A furtherparticular object isv to afford an automatic control of combustionthrough the joint and several regulation of the primary andv secondarystreams; for example through connections whereby the furnace conditions,such as boiler steam pressure and the CO content of the flue gas, mayeffect the desired regulation and thus maintain the combustion inharmony with the service and operation of the furnace or boiler. Otherand furs, 1927. Serial No. beam.

ther objects and advantages of the present invention will be explainedin the hereinafter following descriptlon of an illustrative embodimentthereof or will be understood to those conversant with the subjectmatter. To the attainment of the aforesaid objects and advantages thepresent invention consists. in the novel s stem of combustion and thenovel features 0 apparatus, method, operation, arrangement, mechanismand structure herein described or illustrated.

In the accompany g drawings Fi 1 is a front elevation partly in diagrampartly broken away, showing a furnace, burner and control mechanismembodying the present invention.

Fig. 2 is a central vertical section of the furnace and burner of Fig.1.

' Fig. 3 is a central section of the burner on a larger scale. Fig. 4 isa front elevation of the burner shown in Fig. 3, partly broken away toshow the interior.

Fig. 5 is a central vertical section of. a modified form of burner. Fig.6 is a similar central vertical section showing another form of burner.Fig. 7 is a detail section view taken on the line 7-7 of Fig. 6.

Referring first to the embodiment shown in Figs. 1 to 4 a boiler furnaceis indicated comprising a setting of any usual character, having forexample a front wall 11, side walls 12, and a rear wall 13 which in somecases may be a bridge-wall, and below the enclosed combustion space orchamber a bottom or door 14. While the walls may be of 35 variousconstruction they are indicated as built up of refractory blocks or firebrick, and having interior air ducts or passages as will be laterdescribed, and with convenient provision, for example by door or opening15 for the removal and discharge of ash or soot accumulating on thefloor or bottom.

The boiler is indicated as comprising a system .of water'tubes 16 whichmay be located directly over the combustion chamber and interconnectedby the usual headers and communicating with the overhead drums 17 fromwhich steam may be drawn through mains 18 for consumption. The presentdisclosure presupposes such usual details as bafile walls and the like.In Fig. l is shown I a conventional uptake 20 constituting the exit forthe. spent gases and products of combustion, and leading to the usualstack.

The pulverized coal or similar suspended fuel may be brought to thefurnace through a pipe 22 from any fuel supply, preferably directly froma pulverizing machine. This pipe is shown furnished with a damper 23 forrestricting and regulating the fuel feed. The primary air and suspendedpulverized fuel may be considered as the fuel stream, subsequently to bemet and combined with the stream of secondary air at the place ofcombustion. The fuel pipe 22 terminates in an elbow 24 directlyconnected to the burner 25 which is shown arranged in a circularaperture in the furnace front wall 11 so as to geliver directly into thecombustion cham- The burner 25 contains a centrally arranged fuel tube26 which is coupled to the elbow 24 and shown supported from a Wallplate 27, which plate may be closed in cases where the secondary isdrawn through wall ducts as herein illustrated. The fuel tube 26separates the wall aperture into a central fuel passage 28 and asurrounding annular air passage 29, which, in the preferred embodimentof this invention, is intended to conduct preheated secondary air to thecombustion point. The air passage 29 is shown surrounded by acylindrical lining or sleeve 30 mounted directly in the refractory wallaperture and preferably connected with the outer wall plate 27. By thisarrangement the fuel laden primary air is conducted centrally anddirected into the combustion chamber, while surrounded by an annularstream of entering preheated secondary air.

According to one feature of this invention a rotary suction means or fan32 is employed having the dual function of propelling, by separateportions of the fan, both the in coming primary or fuel stream and thesurrounding secondary or air stream. This two-purpose fan or rotor isshown located directly at the mouth or exit of the burner, and itsdetails of structure and operation will be described at a later point.The fan rotor is shown as having a flaring hub 33 mounted at the innerend of a driving shaft 34 which extends through a ball bearing 35supported within the tube 26 and sealed to exclude fuel. Outwards ofthis bearing the shaft carries a screw blade or vane 36 arranged topropel the fuel through the tube.

.The outer end of the shaft is mounted in a bearing 37 in the elbow 2aand at its outer extremity is provided with suitable drivingconnections, such as a sprocket wheel 38 driven by a chain 39 from asprocket wheel 40 on the shaft of a driving motor H, for example anelectric or other controllable motor.

The dual suction fan 32, operating both on the primary current of airand fuel and upon the secondary air current, may be constructed indifferent ways, but preferably com prises, mounted on the hub 33 orshaft 34, a set of primary vanes, blades or portions 4; in line with theexit of the primary passage or fuel tube, and secondary blades orportions ll at the mouth or exit of the annular secondary orsupplemental air passage 29.

Each set of blades or blade portions is preferably so designed as toproduce both a propelling force, which draws the current through thepassage and delivers it into the combustion chamber, and a rotary orwhirling force tending to create, directly at the mouth of the passage,a fast whirling action and resulting centrifugal force. The blades orblade portions for the two passages are preferably designed especiallyeach for its own function, and therefore operate separately to inducethe correct relative supplies of fuel and air, although the two areshown mechanically connected together as an integral whole: Thestructure, for example maybe as illustrated in Figs. 3 and st whereinthe primary blades 43 are mounted on the hub 33 and extend outwardly toa connecting ring or short cylinder 45 from theouter side of whichspring the secondary blades 44, the extremities of which may in turn beconnected and strengthened by an outer ring or short cylinder 46. As aresult of this arrangement the inner and outer fans, for any givenadjustment of the primary and secondary dampers, will operate to inducerates of flow through the primary and secondary passages which willpreserve a substantially predetermined ratio or relation notwithstandingchanges of fan speed as the latter may be adjusted to suit variations inthe combustion rate or service of the furnace.

' As already stated, this invention preferably employs preheatedsecondary air of combustion, and for this purpose the secondary passage29 may be connected with or piped to any suitable preheater or source ofheated air, preferably'a preheater built with the furnace walls. Withadvantage the invention preferably employssecondary air preheated in theinterior of the walls of the furnace, and to this end the followingprinciples of construction may be employed. The cylindrical iron liningsleeve 30 is shown as formed with a number of air ports 49, ten of thembeing shown, and the refractory tiling 31 outside of the lining issimilarly ported. In connection with this arrangement is shown a rotarydamper or ring 50 having corresponding ports 51, shown in Figs. 3 and 4as in a nearly full open position; adjustment therefore of the damperring regulates the rate at which the fan may draw secondary air throughthe setting for combustion purposes.

' with recesses, passages or ducts for the'flow 'thercfrom isrcdelivered into the furnace of secondary combustion air.- Thus"surrounding the ports 49 are shown a number of wall recesses 52extending outwardly and connecting by a series of lateral passages 53with front wall air ducts 54. These front .wall ducts or channels may besubstantially preferably in a manner to connect in series the ducts inthe respective walls. At the upper part of the front wall 11 may beinlets 55 for the direct admission of atmospheric air to the duct 54 andcontrolled by dampers 56, thus cooling and utilizing the upper rtion ofthe front wall. Each furnace si e wall may be formed with ducts 58,indicated by dotted lines in Fig. 2, each of these being fed withatmospheric air through damper controlled inlets 59. The bottom wall 14is shown formed with interior air ducts 61 having air inlets 62 atvarious points controllable by separate dampers 63. The bottom duct 61is shown as discharging into the lower end of the front wall duct 54.The rear wall 13 is shown provided with a duct 64, fed by inlets 65,controlled by dampers 66; the air being admitted at the upper part ofthe rear wall and flowing downwardly to the foot thereof and thence intothe bottom wall duct 61. In this way all five of the refra'ctory wallsof the furnace are provided with air ducts through which atmospheric airtravels eventually to the burner 32. Each of the walls is'thusinteriorly swept with a constant stream of cooling air to the protection of the wall, while the heat extracted with the secondary air fedto the combustion point.

While in some cases it may be suflicient to have hand adjustment of thering damper 50, it is one feature of this invention that said damper maybeautomatically adjusted to regulate the supply of preheated secondaryair in accordance with the combustion con-' dition and requirements. Theconnections for shifting the damper may be as follows. The ring 60 isshown with opposite lugs 69 which carry posts 70 extending outwardlythrough curved slots 71 to exterior points.

The outer ends of the posts are shown connected by links 72 to a damperoperating lever 73 fulcrumed at 74. This lever is seen in Figs. 1 and 4to extend leftward where its extremity may be swung upwardly anddownwardly by means of a link 75 to adjust the damper. The linkconnectsat its lower end with a bell crank lever 7 6' referably by means of anadjustable pivot 77 permitting the throw to be-varied. The bell crank isshown mounted on a bracket 78 upstanding.

from a box or frame 79 which carries a motor 80, preferably electric,through which the bell crank and connections are to be actuated foradjusting the damper 50. The connections from the motor to the bellcrank may comprise a pinion 81 on the motor shaft engaging a gear 82 bywhich the speed is reduced, this gear being carried by a threaded shaft83 taking its bearings in the bracket 78 and a bearing 84. Surroundingthe screw shaft 83 is a threaded block or traveling nut 85 having a pinand slot connection 86 with the yoked lower end of the bell crank lever.By this arrangement when the motor is operated to turn in one directionor the other it will correspondingly throw the bell crank lever and thuseffect the progressive opening or closing of the damper, and thus adjustthe air supply to the requirements.

The damper adjusting motor 80 may itself be controlled automatically invarious ways, for example from an indicator of the CO content of theflue gases, such as the pointer or index of a C0 meter; and Fig. 1contains a diagrammatic illustration of the principlesof thearrangement. A pipe 89 is shown arranged to conduct flue gas from thestack or uptake 20 to a conventionally shown CO meter 90; this having ascale or dial 91, and an index or pointer 92 with which the controlconnections are intended to cooperate. The meter is shown with thepointer at 14.5 on the assumption that this is a fair or safe average COreading for a furnace of the type to be regulated. The tip of thepointer or hand 92 is shown as provided with a light delicate contact orleaf spring 93 arranged to come in contact with one or another of twostationary but ad'ustable leaf contacts 94 and 95 when the C 2percentage varies below or above the desired average. Fig. 1 showsdiagrammatically an electric conductor or wire a from the index orfinger 92, a wire I) from the contact 94, and a wire 0 from the contact95, these three wires extending from the CO meter to the motor controlmeans next to be described. The preferred plan of action issubstantially as follows. When. for example, the CO content becomesdeficient the contacts 93 and 94 will meet, thus closing the circuitsthrough the conductors a and b, which will operate through the controlmotor 80 to close further the damper 50 and thus decrease the excessiverate of supply of preheated secondary air. This will have asubstantially immediate effect on the com bustion, and a quickcorrection of the CO content, the meter responding with fair promptness,thus reversing the movement of damper. \Vhen the CO content becomes toohigh, indicating shortage of air and too hot combustion the reverseactions take place, the damper being shifted in a direction toincreasethe rate of supply of secondary air. By the described automaticcontrol the damper 50 may be in oscillating adjustment, synchronouslywith the shift of the CO meter between 14 and 15, and in a manner tomaintain the CO content substantially be tween these percentages, orsuch other percentages as may be determined by the positions at whichthe contacts 94 and 95 are applied upon the dial 91.

The connecting means between the 00 meter 90 and the damper motor 80 maycomprise a battery 96, first and second solenoids 97 and 98, first andsecond switches 99 and 100, and wiring as follows. The battery 96 isinterposed between the wire a and a wire at which is branched into wirese and f, the branch 6 extending to the solenoid 97 and the branch f tothe solenoid 98, the other terminals of the solenoids being connectedrespectively with the conductors b and 0, so that when the CO contentdrops to 14% the circuit is connected through the wires a, d, e and b toenergize the solenoid 97 which thereupon closes the switch 99, whilewhen the CO content is excessive and rises to 15% the contacts willcomplete the circuit through wires a, d, f, and c to cause theenergizing of solenoid f and the closing of switch 100.

The positive and negative line wires 9 and h for the motor 80 may extendfrom any source, preferably direct current, of electrical power. Thewires 9 and it pass respectively to the two poles of each of the twoswitches 99 and 100. Assuming now the switch 99 to be closed, by unduelowering of CO content, the line current will be supplied to the motoras follows. The positive counter pole of the switch 99 is shownconnected by wires 2' and branch wire j to one post or brush terminal 17of the motor. while the negative counter pole of the switch 99 isconnected by wire Z to a limit switch m, which in turn is connected bywire n and branch wire 0 to the other brushterminal p of the motor. Inthis way when the CO indicator indicates a low percentage the motor willbe energized by positive current at the terminal 7c and negative currentat the terminal 79 thereby to drive the motor in one direction, namelysuch as to operate the feed screw 83 to swing the bell crank 76 to theright and thus elevate the damper lever 73 to close further the ringdamper 50, which decreases the supply of secondary air to the combustionpoint, and thus increases and restores the proper CO conditions.

in the opposite direction to the motor. The

positive counter pole of the switch 100 is shown connected by wires qand 0 with the terminal 1) of the motor. The negative counter pole ofthe switch is connected by wire 1' with a limit switch 8 which in turnis connected by wires 25 and with the other motor terminal 70. The motoris of such character that reversal of the current reverses the directionof rotation, so that in this case the bell crank lever 76 will be thrownto the left, and the damper lever 73 depressed to open further the ringdamper 50 and increase the rate of supply of secondary air, thustempering the combustion with additional excess air and lowering the COcontent to the predetermined advantageous percentage.

The limit switches m and s are safety devices limiting the throw of thenut 85, bell crank 76, lever 73, and damper 50, namely, by breaking thecircuit to the motor 80 by pressure of the nut 85 upon each of the limitswitches, and the opening thereof, as the ad justment approaches thelimit of movement.

Another cooperative feature of the present invention is the preferablyautomatic regulation of the operation or speed of rotation of the fan orfans which draw fuel laden air and preheated secondary air through thepassages 28 and 29 respectively and project them whirlingly into thecombustion chamber. Such automatic control is herein illustrated by asystem of regulating the speed of the fan shaft in accordance withchanges of pres sure in the delivered steam, the speed being reducedwhen the pressure exceeds a predetermined amount, and vice versa. Thispart of the invention is shown diagrammatically in Fig. 1 and may bedescribed as follows.

The speed of the fan driving motor 41 may be varied through a regulatoror rheostat 104 having its terminals connected with the motor throughwires 105. The rheostat is provided with a series of contact points 106adapted to be successively contacted by a contact arm 107 to vary theresistance of the device and thereby control the current. passing to themotor and the speed of the latter. The rheostat arm 107 is shownconnected by a pitmanor rod 108 with the cross head of a piston rod 109operated by a piston 110 movable in a cylinder 111 having its portscontrolled by a slide valve 112. The valve stem 113 is shifted by a bellcrank lever 114 which in turn is connected by,.a link- 115 with acontrol lever 116 having a weight 117 tending to depress it, while adiaphragm 119 in a case 120 is arranged to lift the lever in oppositionto'the weight. A steam pipe 121 conveys the pressure of the outgoingsteam 1. the burner.

in pipe 18 to the diaphragm case, controlled by a cock 122. Thecasing ofvalve 112 and the cylinder 111 are supplied with steam, water or otherfluid from any source of pressure through a pipe 124. The valve controlsthe admission of fluid to either end of the cylinder so as to operatethe piston and adjust the rheostat, while the fluid from the other endof the cylinder escapes through exhaust pipes 125. When the steampressure is excessive the diaphragm lifts lever 116, which throws valve112 to the left, admitting fluid to the left end of cylinder 111,causing the piston and rheostat arm to shift to the right, thusincreasing the resistance and reducing the current, to slow the motor41, and so reduce the supply of both fuel and air, and slowing down thecombustion. Cooperatively, a damper 127 in the uptake flue 20 maybefurther closed with excess steam pressure by a rope or chain connection128, passingover pulleys 129 and attached to the piston rod 109. v I

The features of the invention and their operation may be reviewed andexplained further as follows. One feature is the induced and regulatedsupply of preheated secondary air to the combustion point, from anysuitable source, specifically through air ducts in the combustionchamber walls, thus cooling the Walls. The supply of such preheatedsecondary air, being efl'ected by the force or suction induced by therotary fan, obviates the usual forced draft created by a pressureblower, and avoids as well the necessity of relying upon an inducedactlon from the primary stream supplied from a p'ulverizer or othersource of fuel laden air.

While thereforethe streams of primary and secondary air are deliveredcooperatively the are independently supplied and'controlle theprimaryair supply being controlled by the action of the pulverizer orother fuel supply means supplemented by the restrictive control of thedamper 23, while the preheated secondary air is, restrictivelycontrolled by the ring damper 50,

The ingredients for combustlon are herein introduced in such a way as toproduce advantageously the short flame, with whirllng action andturbulence, as stated. The WhlIl is produced by the fan, and this islocated at the delivery point of the burner instead of at a point orpoints substantlally within By creating the whirling action directly atthe mouth of the burner, where the combustion begins, it becomes highlyeffective for the purposes hereof. Both the central stream of fuel ladenair and the annular stream of secondary air are whirled rapidly so thatcentrifugal force causes them to flare out fromthe axis of the burnerinto the chamber, producing a wide angle cone of flame, and intimatelymixing the ingredients close to the burner so as to bring about quickcated by the arrowsin Fig. 3, the

and thorough combustion, which is completed in a quite brief space oftime and travel. The resulting flame for example resembles thatapproximately illustrated in Fig. 2, combustion being completed beforeimpingement upon any wall.

The dual acting burner fan is of substantial advantage for carryin outthese operations. One set of fan bla es or portions 44 operates in theannular space conducting secondary air to the combustion point, whilethe other set 43 operates at the delivery of the fuel feeding tube, andthese two sets of blades are connected to turn in unison, so that anyvariation of speed and action is caused to take placecorrespondingly'for the two streams. Conveniently the two blade sets areon the same operating shaft and constitute a single rotary member orrotor. It will be understood that initially the respective fan bladesare to be designed so as to afford the desired predetermined ratios ofsuction or delivery action. The respective blades are shown as set atangles somewhere between 35 and but the angle may be considerablyaltered to suit the conditions at hand. For example the blades may betilted to a very slight 'angle from the plane of rotation in which casea flame approaching the so-called long flame can be produced, consistinof a central stream of fuel laden air riven straight into the furnace inan suitable direction and enveloped by secon ary air, with progressivecombustion continuing for a substantial period. If the blades are tiltednearly to the other extreme, that is, almost parallel to the axis, eachentering stream will be given the maximum whirling action but minimumaxial projectionfrom the burner. Ordinarily angles of blade and anaction intermediate of these is the most desirable. A

differential arrangement is preferred as indiprimary stream receivinggreater whirl an wider angle of spread, and the secondary stream lesswhirl'but more inward propulsion, resulting in an intersecting action.The combined arrangement sucks into the burner the respective componentsand whirls them while projecting them inwardly, as described, thuscreating the short type of flame shown, with its extreme turbulence,quick mixing and rapid combustion.

The automatic adjustment of the speed of the burner fan is believed tobe broadly new, especially with a dual acting fan as described, andespecially under regulation of the degree of steam pressure in theboiler; This regulation of burner action is advantageousin improving thecombustion action of the furnace. When higher service is required of agiven boiler and furnace, calling for higher rates of combustion offuel, and tendency to higher temperatures, the resulting lowered steampressure will bring about the increase of speed of the burner fan. Thishigher speed not only cooperates in affording a higher rate of fuel feedthrough the central tube, but cooperatively supplies increasedquantities of secondary air for the increased combustion, assistinggreatly in preserving the required proportions; while such increasedflow of secondary air through the furnace walls further affords acooperative increased cooling action on the walls. The greater thetendency to overheat the walls the greater is the cooling action on thewalls, which are thus kept within a comparatively steady range of safetemperature. On the other hand in times of low service, when the fueland secondary air are supplied at lower rates, an advantage results inthat the secondary air, traveling more slowly through the furnace walls,is caused to preheat to a relatively greater degree due to the greatertime element in its travel, thus enhancing efficiency.

The regulating feature consisting of means for automatically adjustingthe secondary air damper 50 is advantageous both in itself and incooperation with the other described features. This automatic regulationis cooperative with the regulation of fan speed, the two togethercontrolling the secondary air supply. The regulation is neverthelessindependent and governed from a separate source, in this caseillustrated by the CO meter. Assuming that the best efficiency of agiven furnace is attained with a C0 content of 14% to 15%, then if thepercentage of CO increases above this amount, the index or pointer ofthe CO meter will close the electrical circuits in a manner to cause anopening of the ring damper and thus afford a greater rate of supply ofsecondary air, bringing the combustion, the furnace temperature and theCO content back to the point desired. This regulation therefore controlsthe combustion efiiciency of the furnace in accordance with the rate offuel supplied from the pulverizer or other source, making the secondaryair supply in a manner self regulating to the fuel supply. Thediaammatic illustration of a connection from the CO indicator to thesecondary damper, for regulating the proportions or ratio of the primaryand secondary streams, is merely exemplary of various connections; forexample on account of the delicacy of movement of the pointer of thegalvanometer of the CO meter it may be preferable to avoid me chanicalcontact therewith, and obviously a mirror may be provided to swing withthe pointer and roject a beam of light along a system of se enium orother light cells, to generate currents which may be amplified orrelayed to perform the damper shifting actions. In any case the damperreadjustment may be slow and gradual so that the CO correction may begradual and may b overtaken by the CO meter action, thus avoidingoscillation of the damper between extreme positions.

The regulation principles thus described may be employed in differentways from the analysis of the outgoing or flue gases; for exampleinstead of operating the control from the CO percentage it may beoperated from the percentage of some other ingredient of the flue gasessuch as hydrogen or CO.

The combined regulations greatly facilitate the control of a furnace byreducing the personal attention otherwise needed for maintainingeconomy. .VVhen at times of overload or high steam demand the steampressure drops this will openfurther the uptake damper 127 and speed upthe dual fan 32, expediting all factors of combustion, the fuel supplybeing supposed to be increased at the same time in any known manner. Ifnow the speeded up fan fails to deliver the correct proportion ofsecondary air this will be manifested by an excess or deficiency of. COcontent in the flue gases, which will act through the CO meter anddamper motor to further open or close the secondary air damper until thecorrect supply is afforded. The fan therefore primarily regulates thesecondary air while the dam-per supplemently adjusts it to the correctfigure. Assuming, for example, a coal supply rate of 1000 lbs. per hour,and that the supplemental or secondary air should be between 3 and 3.3pounds per pound of coal; if the fan should feed air only at the rate of3 pounds per pound of coal, or 3000 lbs. of air per hour, this deficientrate would cause an increase of CO content, and when the CO indicatorreaches 15 the ring damper will be opened further and increase thesecondary air supply rate, but when the latter reaches 3300 the COcontent becomes again reduced, the indicator shifting toward 1 1, andupon reaching 14 causing again the further closing of the damper; thusaffording a continuous correction of combustion factors.

Referring next to the modification shown in Fig. 5, this embodiescertain of the underlying features already described, including thesupplying of preheated secondary air from the furnace walls to thecombustion point, and the dual fan assisting the flow of both theprimary and secondary streams; although the burner in this case, insteadof delivering directly into the main combustion space, delivers into apreliminary space or ignition chamber wherein, with thorough mixing ofall of the ingredients of combustion, a large part of the combustionwilltake place, resulting in intense heat in this chamher, which thereupondelivers the flame whirlingly into the main combustion chamber. The wall11 is apertured to form the ignition chamber 135, which is shown ofVenturi-shape, tapered and flaring. Th

pulverized fuel may be supplied through a pipe 22 connecting by an elbow24 with the burner 25 which is set outwardly as com pared with Fig. 3 soas to occupy no part of the ignition chamber 135. The burner comprisesthe central fuel tube 26 which may be cast integral with -the wallelements bounding the secondary passage, and this casting may besupported on a metallic wall plate 27 The fuel tube .26 encloses thefuel passage 28*, and surrounding it is the annular secondary airpassage 29.

As in the first embodiment there is av dual acting fan 32 mounted on ashaft 34 driven by sprocket 38, the shaft being enclosed within a sleeve136, with ball bearings between, the sleeve having a conical inner end137 having substantially the same .flare as the mouth of the primarytube 26. The fan has the primary blades43 and secondary blades 44delivering fuel and air into the chamber 135 in a manner to give aviolent mixing action with high degree of combustion, the flame beingprojected into the main combustion chamber. The annular or secondarypassage 29 is shown supplied with preheated air by curved pipes 52leading from lateral passages 53". connecting with the wall ducts 54, sothat, as before, the air preheated in' the furnace walls is suppliedthrough the described passages to the combustion point.

The modification shown in Figs. 6 and 7 differs principally in thelongitudinal enlargement of the ignition chamber 135", the

burner 32" being set out far beyond the'wall 11*. The pipe 22 and elbow24" conduct the pgimary stream to the burner 25*, the elbow ingconnected to the central fuel tube 26 containing the fuel passage 28 andsurrounded by the secondary air passage 29". The fan 32' mounted onsprocket-driven shaft 34 comprises the primary and secondary blades 43and 44 The shaft is surrounded by sleeve 136" flared at 137 Guides 52conduct the secondary air to the annular assage from an annular passage140 formed etween a large cylindrical casing 141 and a cylindrical wall142 of tiles, the two being bonded and spaced by spacing elements 143.

The cylindrical wall 142 bounds the ignition chamber 135". The preheatedair from the wall ducts 54 passes through lateral recesses 53* into theannular channel 140 and thence to the annular passage 29. As in thefirst described form the fan blades 43 and 44" may be designed to causeintersecting primary and secondary streams.

The forms of apparatus and method which are herein illustrated but notmade the subject of specific claim are not intended to be disclaimed butare reserved for claim by divisional application or otherwise.

There has thus been described a system of combustion of pulverized orsimilar fuel embodying the principles and attaining the objects of thepresent invention; Since various matters of apparatus,method,'operation, arrangement, mechanism and structure may be modifiedwithout departing from the principles of the invention it is'notintended to limit the same to such matters except so far as set forth inthe appended claims.

What is claimed is:

* .1. A burner for fluent fuel comprising a control passage for fuelladen air, a surrounding passage for secondary air, and rota meansoperating at the delivery ends of 0th passages for positively whirlingand delivering both streams and causing. them to combine in a wide angleshort flame.

2. Apparatus for combustion of fluent fuel, comprising an interiorprimary passage for a stream of primary fuel laden air-and a surroundingsecondary passage for a stream of secondary air, rotary suction devicesor blades at the delivery ends of said respective passages, and meansfor driving the respective suction devices in-unison to pull, whirl anddeliver to the combustion point the primary and secondary streams in apredetermined relation.

.3. Apparatus asin claim 2 and wherein.

the drive means are adjustable to vary simultaneously andcorrespondingly theaction of the suction devices for controlling bothstreams adaptably to changes in combustion conditions.

4. Apparatus as in claim 2 and wherein the suction and delivery devicesare such as to deliver both whirling streams at diverging angles but sothat one impinges upon the other for rapid mixing and combustion, and ashort turbulent flame.

i 5. Apparatus as in claim 2 and wherein the combustion space into whichthe flame is delivered is surrounded by walls having air passagesconnected to supply preheated air to the secondary passage to be drawntherethrough by the suction device at the mouth thereof. i

6. A burner asin claim 1 wherein the rotary whirling means for the twostreams are interconnected to be driven in unison, a single drivingmeans for both, and means for varying the speed thereof.

7 In a boiler furnace, a burner delivering a stream of fuel laden airand a stream'of secondary air to the combustion point, power means forpositively drawing, whirling and injecting both said streams into thecombustion space, a controller regulating the speed of said power means,and a steam pressure responsive device for regulating such controller.

8. Apparatus as in claim 2 and a boiler heated by the combustion, a'pressure responsive device operated by the boiler pressure, and acontroller operated by said dewherein is vice for automaticallyregulating the means driving the suction devices.

9. Apparatus as in claim 2 and wherein is a boiler heated by thecombustion, a pressure responsive device operated by the boilerpressure, and a controller operated by said device for automaticallyregulating the means driving the suction devices, and an uptake dampercontrolling the flow of outgoing gases, with means operated by thepressure responsive device for adjusting such damper.

10. The method of controlling a boiler furnace comprising jointlyregulating the admission of fuel laden air and secondary air accordingto the steam pressure and separately regulatingthe proportions thereofaccording to the CO content of the flue gases.

11. In a furnace burning pulverized fuel separate passages conducting tothe combustion point a stream of fuel laden primary air and a secondaryair stream, a control means for adjusting the relative supply of therespective stream, a C0 measuring means, and connections therefrom foroperating said control means to increase the proportion of secondary airupon increase of CO content and vice versa.

12. Apparatus for combustion of finely divided fuel in suspension in aircomprising a fan sucking, whirling and delivering the ingredients intothe combustion space, power means driving such fan, means for varyingthe action thereof, means controlled by the effect of combustion forautomatically regulating such variation, and supplemental means,controlled by the CO content of the flue gases, for automaticallyregulating the proportions of air and fuel delivered to the combustionpoint. p

13. In a boiler furnace fired by fluent fuel means supplying a stream offuel laden primary air. means supplying a stream of secondary air,regulating means operated by the steam pressure for jointly regulatingboth said'supply means, and se arate regulating means operated by the C2 content of the flue gases for relatively regulating the operations ofsaid supply means to vary the proportions of said streams.

14. Method of combustion of fluent fuel for steam generation comprisinga supplying a central primary stream of fuel laden air and a surroundingstream of secondary air, positively drawing, whirling and deliveringboth streams with forward movement to combine in the combustion space,and automatically regulating the drawing, whirling and delivering ofboth such actions conjointly by increase of such action upon decrease ofsteam pressure and vice versa.

15. Apparatus for combustion of fluent fuel comprising concentricpassages delivering the fuel and air, a fan occupying the delivery endsof both said passa es for sucking, whirling and delivering therespective ingredients into the combustion space, power means drivingsuch fan, means for varying the speed thereof, and means controlled bythe effect of combustion for automatically regulating such variation,and thereby the delivery of both fuel and air.

16. Method of combustion of fluent fuel comprising delivering a streamof fuel laden primary air and a stream of secondary air. to combine atthe combustion point, restrictively adjusting the secondary air flow inrelation to the primary air between the source and delivery point, andautomatically regulating such adjustment by the combustion results.

17. In a fluent fuel combustion apparatus means supplying a stream offuel and primary air, means supplying a stream of secondary air, a C9,meter, and means operated by the meter acting upon said supplying meansfor adjusting the relative proportions of such two streams.

18. Means for the combustion of fluent fuel comprising walls defining acentral passage delivering under pressure a central stream of fuel ladenair and outer walls defining an annular passage surrounding said centralpassage for delivering a stream of secondary air to the combustionpoint, and rotary means positively whirling in the same rotary directionat the delivery point both the fuel laden central and the secondary airannular streams, whereby they issue with both axial and spreadingmovement, thereby creating awide angle short flame with quick mixing andturbulent combustion.

19. Apparatus for the combustion of fluent fuel, comprising separatepassages delivering fuel laden air and secondary air inwardly to thecombustion point, the secondary air passage having an inlet dampercontrolling the flow, and a rotary device operating in the secondary airpassage closely in advance of its delivery to the combustion point forforcing the flow of secondary air, said rotary device having poweractuating means, and means for varying the forcing action there of tocontrol the flow of secondary air.

In testimony whereof, I have affixed my signature hereto.

' STEPHEN M. FINN.

